furious recording technologies

fracsid

 

Prologue

 

 Somehow, although I managed to convince myself to drop the $$$ on an Elektron MD and MnM, I could never justify dropping $900 on a Sidstation.  Looking around online, I found uCApps's midibox SID, and specification wise, it was outstanding!  Kits were easy to acquire (all but the AOUT board) from SmashTV at Coinoptech.

 

 

 

 

Just after completing my PAIA 9700 modular, I had another look at the midibox page, and found that Thorsten had just built an analog output board to control VCF's.  The midibox core module already accepted 6 analog CV inputs... ideal for use in my modular synth.  So I ordered up a bunch of board kits, a bunch of expensive Molex connectors, ribbon cable, and an LCD.  Total cost ended up somewhere around $200.

 

The AOUT board was difficult to get (had it shipped from Germany), with expensive DAC's.  There is a new low cost AOUT board up on uCApps - but I haven't had a reason to try it.

 

           Top left - AOUT module

           Bottom left - DIN Module (for input switches and rotary encoder)

           Top right - power board (homemade obviously)

           Middle right - SID board

           Bottom Right - Core Module

I chose to cram all of this into a 3U Frac panel... it wasn't easy!  I used frontpanel express to layout the panel, but hadn't figure out that printing the end result and using it to drill holes makes life so much easier.  I laid this one out with a ruler and a Sharpie... not pleasant - and of course the I/O jacks are a bit wonky.  I had intended to order a finished panel from FPE, but... I'm too lazy and too cheap.  There isn't really enough room on it for me to dry transfer labels, and the layout is simple enough that I can remember what's what.

 

Between Thorsten Klose's excellent website, and the additional info / beautiful diagrams at Coinoptech, I managed to figure out the board to board wiring of this beast.  Wasn't trivial, and it took a lot of scrawled notes and attention to detail, but it worked without too much time spent debugging.  The midibox user group was very, very helpful.

 

Because the input/output specs of this synth are not at typical modular levels, I built a CGS60 stompbox adapter that sits in a single unit frac-panel next to the module.  This amplifies the output by 2X and divides any signals I want to send through the SID by 10.  Works great... a must have.  I didn't incorporate it into my design because it is useful to have the CGS60 around even when I'm not using the fracsid.

 

 

 

 

Final product is fantastic - it really adds a lot of flexibility to my modular synth.  One of its strongest features is that its code is open source.  Thorsten provides you with all of the code, and you have to modify it and compile it to reflect the I/O options you built.  So, not only have I built a SID module, but I can upload things like a program that speaks with ASidXP, so that I can play the 1000's of SID tunes available on the web.  Or even better, I can upload the Midibox CV code to it and use it as a fairly sophisticated MIDI to CV converter.  And, if I had a more recent, decent OS on my PC, I could modify it to do things like quantize the inputs, and mix CV's/LFO's.  In the hands of a competent, motived programmer (not me by any stretch), this module could rival the PSIM-1.

 

 

 

So, what does it sound like?  I put together some stripped down presets for use in my modular, and recorded a few samples of these.  I didn't clean up the sound much if any on these samples - if you want clean noise free sound, don't bother building this module.  The noise adds character!

 

A simple unprocessed sawtooth oscillator sound.

A simple square-wave oscillator.

A simple noise source.

 

For some reason, running multiple oscillators at once, the oscillators drift in phase, giving some really nice phase effects - very SID sounding.

 

Here are samples of the saw and square waves filtered by my EFM VCF-2F (Moog ladder) module.

 

Here is a Blacet Miniwave oscillator run through the SID's dirty filter.